This invention relates generally to sealing between two relatively articulable surfaces and more particularly to sealing between a stationary vat wall and an articulating baffle.
In processing of wood pulp for papermaking, various washing and filtering operations are required. In these and other operations, it is necessary to separate fluids having different levels of contamination or different concentrations. Frequently, this will require a long seal across a substantial gap between two parallel relatively articulable surfaces, e.g., separating pulp slurry from washing liquid contained on opposite sides of a pressure filter stationary housing wall and a cooperating articulable compaction baffle member.
Commonly, this type of seal is made by attaching a piece of elastomeric material to and between the two relatively articulable surfaces. The seal dimensions and configuration are important factors in providing necessary flexing, differential pressure resistance, differential expansion load bearing, and longitudinal joint sealing and attachment stiffness; the materials of construction must be resistant to chemical attack and flexing. In addition, because of the magnitude of the length of the seal, and the relative variations in gap, joint surface, and parallelism, the temperature, the pressure, and the relative motion between the two surfaces; the elastomeric material must be quite thick - -- often 3/8" or more. Repeated flexure of a thick member results in high surface stresses due to the distance of the surfaces from the neutral axis of the flexible member. Such high stresses often result in premature tearing and splitting of the seal and/or failure of the fixing, holding, and/or seal clamping mechanism. In addition, fluid pressure, temperature, and chemical activity, as well as local extremes of stress due to non-uniform (or kinked) flexure shorten the service life of the seal member. Seal failure may result in degradation of pulp cleanliness and resultant quality due to premature intermixing of pulp slurry with wash liquid through the broken seal. Tearing/splitting failures can result in pieces of the elastomeric seal material being discharged to further processes such as paper making where such material will detrimentally affect the paper machine components and/or result in non-salvable paper. Seal replacement requires shutdown of the equipment and its attendant production loss.
The foregoing illustrates some of the limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.